Constant velocity ball joint as a counter track joint

ABSTRACT

A constant velocity ball joint in the form of a counter track joint, having an outer joint part, an inner joint part, torque transmitting balls received in pairs of tracks formed of outer tracks and inner tracks, and a ball cage. First pairs of tracks whose first control angles open in a first axial direction hold first balls. Second pairs of tracks whose control angles open in a second axial direction hold second balls. The control angles are defined as angles between the tangents at the ball contact points in the pairs of tracks. The outer joint part and the inner joint part are axially displaceable relative to one another. The first control angle and the second control angle change in opposite senses when a relative axial displacement occurs. The axial displacement path is limited to observing a minimum value of at least 8° for the respective smaller control angle.

TECHNICAL FIELD

The present invention relates to a constant velocity ball jointpermitting axial displacement.

BACKGROUND OF THE INVENTION

The most frequent type of plunging joints are so-called VL joints(cross-groove joints) such as according to U.S. Pat. No. 4,678,453wherein the center lines of the outer tracks and of the inner trackseach form oppositely directed angles of intersection with thelongitudinal joint axis and are positioned in planes extending parallelto the longitudinal joint axis or on a cylindrical face around thelongitudinal joint axis.

From U.S. Pat. No. 3,133,431, there are known plunging joints whereinthe center lines of the outer tracks and of the inner tracks formidentically sized angles of intersection with the longitudinal jointaxis, i.e., they are positioned in planes which contain the longitudinaljoint axis itself.

Both the above-mentioned types of joint are joints with straight tracks.

It would be desirable to provide a new type of plunging joint for largearticulation angles and relatively short displacement paths.

SUMMARY OF THE INVENTION

The present invention provides a constant velocity ball joint in theform of a counter track joint. The joint includes an outer joint partwith outer tracks, an inner joint part with inner tracks, torquetransmitting balls which are received in pairs of tracks consisting ofouter tracks and inner tracks which are curved outwardly with referenceto the longitudinal joint axis A, and a ball cage with cage windows inwhich the balls are held in a common plane and are guided on to theangle-bisecting plane when the joint is articulated. First outer tracks,together with first inner tracks, form first pairs of tracks whose firstcontrol angles β₁ open in a first axial direction and in which firstballs are held. Second outer tracks, together with second inner tracks,form second pairs of tracks whose second control angles β₂ open in asecond axial direction and in which second balls are held. The controlangles β₁, β₂ are defined as angles between tangential planes at theball contact points in the tracks. Further, the outer joint part and theinner joint part are axially displaceable relative to one another andthe first control angles β₁ and the second control angles β₂ change inopposite senses when a relative axial displacement occurs. The axialdisplacement path V_(max) is limited to a maximum value that produces aminimum value of at least 8° for the respective smaller control anglesβ₁, β₂. The present joint provides an axial displacement path having atleast 0.8 mm, and preferably more than 1.0 mm of play. This issubstantially above the axial play of fixed joints, which in comparisonis at most 0.5 mm.

In one form of the displacement path, the joint In accordance with theinvention provides a way to uncouple axial vibrations and thuscontributes towards improving the noise, vibration, harshness (NVH)behavior. The present design is also advantageous in that it is possibleto un-fine the surfaces during the machining operations. Also, thedesign of the tracks provides a joint with axial centeringcharacteristics.

In particular, the tracks are curved as in Rzeppa joints orundercut-free (UF) joints. As a consequence, even with largerarticulation angles, there is achieved adequate ball control due tosufficiently large control angles.

By limiting the axial displacement path, it is ensured that the controlangles do not become too small as a result of the axial displacement.The stops for delimiting the axial plunging path can become effectiveexclusively between the outer joint part and the cage, or exclusivelybetween the inner joint part and the cage, or between both pairssimultaneously; in each case when the joint is in the aligned position,in which case the longitudinal axes of the inner joint part and of theouter joint part coincide. As the ball cage is radially set freerelative to the inner joint part and to the outer joint part, the jointis characterised by particularly low friction. Furthermore, because ofthe counter-track formation, it is ensured that the joint is axiallyself-centering and that the forces acting on the cage are kept withincertain limits. In addition, the way in which the balls are enveloped bythe tracks in a cross-sectional view is particularly advantageous.

Other advantages of the invention will become apparent upon reading thefollowing detailed description and appended claims, and upon referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this invention, reference shouldnow be made to the embodiments illustrated in greater detail in theaccompanying drawings and described below by way of examples of theinvention.

In the drawings, fixed joints with counter tracks are compared withinventive joints; both will be described in detail below.

FIG. 1 shows a prior art fixed joint with counter tracks according tothe state of the art, having Rzeppa tracks: (a) in a longitudinalsection through a pair of counter tracks; (b) in a bent longitudinalsection through a cage web.

FIG. 2 shows a prior art fixed joint with counter tracks, havingundercut-free (UF) tracks: (a) in a longitudinal section through a pairof counter tracks; (b) in a bent longitudinal section through a cageweb.

FIG. 3 shows an inventive joint in a first embodiment with Rzeppa tracksin a bent longitudinal section through a cage web.

FIG. 4 shows a detail X of FIG. 3 in an enlarged scale: (a) in anaxially centered position of the joint; (b) with maximum axialdisplacement of the joint.

FIG. 5 shows an enlarged detail of a joint similar to that illustratedin FIG. 3 with maximum axial displacement: (a) in a first modifiedembodiment; (b) in a second modified embodiment.

FIG. 6 shows an inventive joint in a second embodiment with Rzeppatracks in a bent longitudinal section through a cage web.

FIG. 7 shows a detail X of FIG. 6 in an enlarged illustration: (a) in anaxially centered position of the joint; (b) with maximum axialdisplacement of the joint.

FIG. 8 shows an inventive joint in a third embodiment with Rzeppa tracksin a bent longitudinal section through a cage web.

FIG. 9 shows the detail X of FIG. 8 in an enlarged scale: (a) in anaxially centered position of the joint; (b) with a maximum axialdisplacement of the joint.

FIG. 10 shows an inventive joint in a fourth embodiment with Rzeppatracks in a bent section through a cage web.

FIG. 11 shows the detail X of FIG. 10 in an enlarged scale: (a) in anaxially centered position of the joint; (b) with maximum axialdisplacement of the joint.

FIG. 12 illustrates the principle of an inventive joint in alongitudinal section through a pair of counter tracks, leaving out theball cage: (a) with maximum axial displacement in a first direction; (b)in an axially centered position of the joint; (c) with maximum axialdisplacement in the second direction.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 refer to prior art joints for comparative purposes and tocomplete the description. They will be described jointly. A joint 11includes an outer joint part 12 with a formed-on journal 13, an innerjoint part 14 with a plug-in aperture 15 for a shaft, balls 16 ₁, 16 ₂and a cage 17 having windows 18 in which the balls are held. The jointsare counter track joints. Thus, first outer ball tracks 19 ₁ in theouter joint part 12 and first inner ball tracks 20 ₁ in the inner jointpart 14, which tracks hold first balls 16 ₁, are designed axiallyoppositely relative to second outer ball tracks 19 ₂ in the outer jointpart 12 and second inner ball tracks 20 ₂ in the inner joint part 14,which tracks hold second balls 16 ₂. The first pairs of tracks 19 ₁, 20₁ have control angles which open in a first direction R₁. The secondpairs of tracks 19 ₂, 20 ₂ have control angles which open in a seconddirection R₂. The counter track formations are achieved in that thecenters of curvature of the outer ball tracks 19 ₁, 19 ₂ in the outerjoint part are circumferentially alternately offset in opposite axialdirections relative to the central joint plane E, and equally, thecenters of curvature of the inner ball tracks 20 ₁, 20 ₂ in the innerjoint part 14 are circumferentially alternately offset in opposite axialdirections relative to the central joint plane E. The central jointplane is defined by the centers of the balls.

The ball cage 17 includes a spherical outer face 21 which is guided in aspherical inner face 22 of the outer joint part 12. Furthermore, thecage includes a spherical inner face 23 in which there is guided aspherical outer face 24 of the inner joint part 14. As a result of thisconfiguration, the joints become fixed joints.

The track center lines 9 ₁, 10 ₁ of the tracks 19 ₁, 20 ₁ as well as thetrack center lines 9 ₂, 10 ₂ of the tracks 19 ₂, 20 ₂ intersect oneanother in the central joint plane E when the joint is in the alignedcondition. Whereas in FIG. 1, the center lines 9, 10 of the tracks areentirely circular arches, the center lines 9, 10 of the tracks in FIG. 2are formed by circular arches with an adjoining axis-parallel tangent.

FIG. 3 shows a joint 11 ₃ which is similar to that shown in FIG. 1 butdiffers substantially in certain details. The details which correspondto one another have been given the same reference numbers. To thatextent, reference is made to the description above. In particular,reference is made to the illustrated outer tracks 19 ₁ and inner tracks20 ₁ as well as to the outer tracks 20 ₂ and inner tracks 20 ₂ which arenot shown in FIG. 3 for simplification. The details which deviate fromFIG. 1 have been given the index 3 and will be referred to below. Withthe joint of FIG. 3, the spherical outer face 21 ₃ of the ball cage 17 ₃is arranged at a radial distance from the spherical inner face 22 ₃ ofthe outer joint part 12 ₃. Furthermore, the spherical inner face 23 ₃ ofthe ball cage 17 ₃ is arranged at a radial distance from the sphericalouter face 24 ₃ of the inner joint part 14 ₃. As a result, there isachieved, as will be explained in greater detail below, a relative axialdisplaceability between the outer joint part 12 ₃ and the inner jointpart 14 ₃, with the ball cage 17 ₃ setting itself to half the path.

In FIG. 4a, in the enlarged detail X of FIG. 3, any detailscorresponding to those in FIG. 3 have been given the same referencenumbers, with reference being made to the previous description.

In FIG. 4b, the enlarged detail X of FIG. 3 is in a modified position,with the central joint plane, in its relative position relative to theouter joint part 12 ₃, being arbitrarily used as the reference planeE_(B). With respect hereto, the inner joint part 14 ₃ is axially movedtowards the right by the displacement path VI, whereas the ball cage 17₃ is moved towards the right by half the size of the displacement pathVC. In this position, an inner edge 25 ₃ of the outer joint part 12 ₃stops against the outer face 21 ₃ of the ball cage 17 ₃, whereas at thesame time an outer edge 26 ₃ of the inner joint part 14 ₃ stops againstthe inner face 23 ₃ of the ball cage 17 ₃. An outer edge 27 ₃ of theball cage and a second outer edge 28 ₃ of the inner joint part formcorresponding stops, with the displacement path of the same sizeextending in the opposite direction. An angle ∝₁ at the ball cage is theangle between the central plane of the ball cage and the line of contactwith the edge 25 ₃, and an angle ∝₂ at the ball cage 17 ₃ is the anglebetween the central plane of the ball cage and the line of contact withthe edge 26 ₃. The radius of the inner face 22 ₃ at the outer joint parthas been given the reference symbol RO and the radius of the face 21 ₃at the ball cage has been given the reference symbol RC.

FIG. 5a shows part of a modified inventive joint similar to thatillustrated in FIG. 4b. Identical parts have been given identicalreference numbers, but are identified by the index 4. As a result ofmodified radii, only one circumferential edge 26 ₄ of the inner jointpart 14 ₄ touches the inner face 23 ₄ of the ball cage 17 ₄, whereas inthis axial stopping position, the outer face 21 ₄ of the ball cage 17 ₄still has radial play relative to the inner edge 25 ₄ of the outer jointpart 12 ₄. A second outer edge 28 ₄ of the inner joint part forms acorresponding stop, with the displacement path of the same sizeextending in the opposite direction. An angle ∝ at the ball cage 17 ₄ isthe angle between the displaced central plane and a radius through thecontacting edge.

FIG. 5b shows part of a modified inventive joint similar to thatillustrated in FIG. 4b. Identical parts have been given identicalreference numbers, but are identified by the index 5. As a result ofmodified radii, only one circumferential edge 25 ₅ of the outer jointpart 12 ₅ touches the outer face 21 ₅ of the ball cage 17 ₅, whereas inthis axial stopping position, the inner face 23 ₅ of the ball cage 17 ₅still has radial play relative to the outer face 23 ₅ of the inner jointpart 14 ₅. An outer edge 27 ₅ of the ball cage forms a correspondingstop, with the displacement path of the same size extending in theopposite direction. An angle ∝ at the ball cage 17 ₅ is the anglebetween the displaced central plane and a radius through the contactingedge.

FIG. 6 shows a joint 11 ₆ which is similar to that shown in FIG. 1 butdiffers substantially in certain details. The details which correspondto one another have been given the same reference numbers. To thatextent, reference is made to the description above. In particular,reference is made to the illustrated outer tracks 19 ₁, and inner tracks20 ₁ as well as to the outer tracks 19 ₂ and inner tracks 20 ₂ which arenot shown in FIG. 6, for simplification. The details which deviate fromFIG. 1 have been given the index 6 and will be referred to below. Withthe joint of FIG. 6, the spherical outer face 21 ₆ of the ball cage 17 ₆is radially centered in an internally cylindrical inner face 22 ₆ of theouter joint part 12 ₆, but has axial play relative to two adjoininginternally conical stop faces 29 ₆, 30 ₆. Furthermore, the inner face 23₆ of the ball cage 17 ₆ is arranged at a radial distance from thespherical outer face 24 ₆ of the inner joint part 14 ₆. As a result,there is achieved, as will be explained in greater detail below, arelative axial displaceability between the outer joint part 12 ₆ and theinner joint part 14 ₆, with the ball cage 17 ₆ setting itself to halfthe displacement path.

In FIG. 7a, in the enlarged detail X of FIG. 6, the same details as inFIG. 6 have been given the same reference numbers, with reference beingmade to the previous description.

In FIG. 7b, the enlarged detail X of FIG. 6 is in a modified position,with the central joint plane, in its relative position relative to theouter joint part 12 ₆, being arbitrarily used as the reference planeE_(B). With reference hereto, the inner joint part 14 ₆ is axially movedtowards the right by the displacement path VI, whereas the ball cage 17₆ is moved towards the right by half the size of the displacement pathVC. In this position, an inner edge 25 ₆ of the outer joint part 12 ₆stops against the outer face 21 ₆ of the ball cage 17 ₆, whereas at thesame time an outer edge 26 ₆ of the inner joint part 14 ₆ stops againstthe inner face 23 ₆ of the ball cage 17 ₆. An outer edge 27 ₆ of theball cage and a second outer edge 28 ₆ of the inner joint part formcorresponding stops, with the displacement path of the same sizeextending in the opposite direction. An angle ∝ at the ball cage 17 ₆ isthe angle between the central plane of the ball cage and the line ofcontact with the edge 25 ₆. The radius of the face 21 ₆ at the ball cagehas been given the reference symbol RC.

FIG. 8 shows a joint us which is similar to that shown in FIG. 1, butdiffers substantially in certain details. The details which correspondto one another have been given the same reference numbers. To thatextent, reference Is made to the description above. In particular,reference is made to the illustrated outer tracks 19 ₁ and inner tracks20 ₁ as well as to the outer tracks 19 ₂ and inner tracks 20 ₂ which arenot shown in FIG. 8, for simplification. The details which deviate fromFIG. 1 have been given the index 8 and will be referred to below. Withthe joint of FIG. 8, the spherical outer face 21 ₈ of the ball cage 17 ₈is radially centered in the cylindrical inner face 22 ₈ of the outerjoint part 12 ₈. Furthermore, the inner face 23 ₈ of the ball cage 17 ₈is arranged at a radial distance from the spherical outer face 24 ₈ ofthe inner joint part 14 ₈. As a result, there is achieved, as will beexplained in greater detail below, a relative axial displaceabilitybetween the outer joint part 12 ₈ and the inner joint part 14 ₈, withthe ball cage 17 ₈ setting itself to half the displacement path.

In FIG. 9a, in the enlarged detail X of FIG. 8, the same details as inFIG. 8 have been given the same reference numbers, with reference beingmade to the previous description.

In FIG. 9b, the enlarged detail X of FIG. 8 is in a modified position,with the central joint plane, in its relative position relative to theouter joint part 12 ₈, being arbitrarily used as the reference planeE_(B). With reference hereto, the inner joint part 14 ₈ is axially movedtowards the right by the displacement path VI, whereas the ball cage 17₈ is moved towards the right by half the size of the displacement pathVC. In this position, an outer edge 26 ₈ of the inner joint part 12 ₈stops against the inner face 23 ₈ of the ball cage 17 ₈. A second outeredge 28 ₈ of the inner joint part forms a corresponding stop, with thedisplacement path of the same size extending in the opposite direction.An angle ∝ at the ball cage 17 ₈ is the angle between the central planeof the ball cage and the line of contact with the edge 26 ₈. The radiusof the outer face 24 ₈ at the inner joint part has been given thereference symbol RI and the radius at the inner face 21 ₈ at the ballcage has been given the reference symbol RC.

FIG. 10 shows a joint 11 ₁₀ which is similar to that shown in FIG. 1,but differs substantially in certain details. The details whichcorrespond to one another have been given the same reference numbers. Tothat extent, reference is made to the description above. In particular,reference is made to the illustrated outer tracks 19 ₁ and inner tracks20 ₁ as well as to the outer tracks 19 ₂ and inner tracks 20 ₂ which arenot shown in FIG. 10, for simplification. The details which deviate fromFIG. 1 have been given the index 10 and will be referred to below. Withthe joint of FIG. 10, the spherical outer face 21 ₁₀ of the ball cage 17₁₀ is radially centered in an internally cylindrical inner face 22 ₁₀ ofthe outer joint part 12 ₁₀. Furthermore, the spherical outer face 24 ₁₀of the inner joint part 14 ₁₀ is centered in the internally cylindricalinner face 23 ₁₀ of the ball cage 17 ₁₀. As a result, there is achieved,as will be explained in greater detail below, a relative axialdisplaceability between the outer joint part 12 ₁₀ and the inner jointpart 14 ₁₀, with the ball cage 17 ₁₀ setting itself to half thedisplacement path.

In FIG. 11a in the enlarged detail X of FIG. 10, the same details as inFIG. 10 have been given the same reference numbers, with reference beingmade to the previous description.

In FIG. 11b, the enlarged detail X of FIG. 10 is in a modified position,with the central joint plane, in its relative position relative to theouter joint part 12 ₁₀, being arbitrarily used as the reference planeE_(B). With respect hereto, the inner joint part 14 ₁₀ is axially movedtowards the right by the displacement path VI, whereas the ball cage 17₁₀ is moved towards the right by half the size of the displacement pathVC. In this position, an inner edge 25 ₁₀ of the outer joint part 12 ₁₀stops against the outer face 21 ₁₀ of the ball cage 17 ₁₀. An outer edge27 ₁₀ of the ball cage forms a corresponding stop, with the displacementpath of the same size extending in the opposite direction. An angle ∝ atthe ball cage 17 ₁₀ is the angle between the central plane of the ballcage and the line of contact with the edge 25 ₃. The radius of the face21 ₁₀ at the ball cage has been given the reference symbol RC.

FIG. 12, in a simplified illustration without the cage, shows the outerjoint part 12, the inner joint part 14 and the balls 16 which carry thesame reference numbers as used in FIG. 1. In all three illustrations,the central plane defined by the ball centers is referred to as thecentral joint plane E, i.e., a new artificial reference plane is notintroduced. The tracks 19, 20 are referred to by their track base linesand their track center lines 9, 10 only. For the sake of simplicity, thetrack edges have also been eliminated. The position of the balls isdefined by the points of intersection of the track center lines 9, 10.As a result of the relative displacement V_(max) between the outer jointpart and the inner joint part, the centers of curvature of the trackcenter lines 9, 10 are displaced relative to one another, as a result ofwhich the control angles between the associated track center lines 9, 10simultaneously change in opposite senses, i.e. the one increases, theother decreases. The minimum distance of the centers of curvature fromthe central joint plane E is referred to as Q_(min) and the maximumdistance of the centers of curvature from the central joint plane E isreferred to as Q_(max). The angles between the radii positionedperpendicularly on the tangents in the points of intersection of thetrack center lines correspond to the control angles β₁, β₂ between saidtrack center lines. Each half of said angles between the radii isreferred to as β_(max/2), β_(min/2). The axial displacement is to bedelimited to such an extent that β_(min)/2 is not less than 4° and thatthe smallest control angle β_(min) thus is not less than 8° In the FIGS.reference letter M represents the center of curvature for the respectiveball tracks having the corresponding number. Thus, for example, M9 ₂ isthe center of curvature of the center lines of the second inner balltracks 9 ₂.

From the foregoing, it can be seen that there has been brought to theart a new and improved constant velocity joint. While the invention hasbeen described in connection with one or more embodiments, it should beunderstood that the invention is not limited to those embodiments. Thus,the invention covers all alternatives, modifications, and equivalents asmay be included in the spirit and scope of the appended claims.

What is claimed is:
 1. A constant velocity ball joint in the form of acounter track joint, comprising: an outer joint part with outer tracks,an inner joint part with inner tracks, torque transmitting balls whichare received in pairs of tracks comprising said outer tracks and innertracks which are curved outwardly with reference to a longitudinal jointaxis, and a ball cage with cage windows in which the balls are held in acommon plane and are guided on to an angle-bisecting plane when thejoint is articulated; first outer tracks, together with first innertracks, form first pairs of tracks whose first control angles (β₁) openin a first axial direction (R₁) and in which first balls are held; andsecond outer tracks, together with second inner tracks, form secondpairs of tracks whose second control angles (β₂) open in a second axialdirection (R₂) and in which second balls are held; wherein the controlangles (β₁, β₂) are defined as angles between tangents at ball contactpoints in the tracks pairs; and wherein the outer joint part and theinner joint part are axially displaceable relative to one another andthe first control angles (β₁) and the second control angles (β₂) changein opposite senses when a relative axial displacement occurs, the axialdisplacement path (V_(max)) being limited to a maximum value thatchanges the control angles (β₁, β₂) so as to be not less than 8° for thesmaller of the respective control angles (β₁, β₂), wherein the axialdisplacement path is delimited in axial stopping positions by end edgesof the inner joint part stopping against a spherical inner face of theball cage, and wherein in said axial stopping positions an outer face ofthe ball cage has radial play relative to an inner edge of the outerjoint part.
 2. A joint according to claim 1, wherein in an axiallycentered position of the joint, the ball cage exhibits axial playrelative to the outer joint part and the inner joint part.
 3. A jointaccording to claim 1, wherein an inner face of the outer joint part isinternally spherical.
 4. A joint according to claim 1, wherein the innerface of the ball cage is internally spherical.
 5. A constant velocityball joint in the form of a counter track joint, comprising: an outerjoint part with outer tracks, an inner joint part with inner tracks,torque transmitting balls which are received in pairs of trackscomprising said outer tracks and inner tracks which are curved outwardlywith reference to a longitudinal joint axis, and a ball cage with cagewindows in which the balls are held in a common plane and are guided onto an angle-bisecting plane when the joint is articulated; first outertracks, together with first inner tracks, form first pairs of trackswhose first control angles (β₁) open in a first axial direction (R₁) andin which first balls are held; and second outer tracks, together withsecond inner tracks, form second pairs of tracks whose second controlangles (β₂) open in a second axial direction (R₂) and in which secondballs are held; wherein the control angles (β₁, β₂) are defined asangles between tangents at ball contact points in the tracks pairs; andwherein the outer joint part and the inner joint part are axiallydisplaceable relative to one another and the first control angles (β₁)and the second control angles (β₂) change in opposite senses when arelative axial displacement occurs, the axial displacement path(V_(max)) being limited to a maximum value that changes the controlangles (β₁, β₂) so as to be not less than 8° for the smaller of therespective control angles (β₁, β₂), wherein the axial displacement pathis delimited in axial stopping positions by circumferential edges in theouter joint part stopping against a spherical outer face of the ballcage, and wherein in said axial stopping positions an inner face of theball cage has radial play relative to an outer face of the inner jointpart.
 6. A joint according to claim 5, wherein in an axially centeredposition of the joint, the ball cage exhibits axial play relative to theouter joint part and the inner joint part.
 7. A joint according to claim5, wherein an inner face of the outer joint part is internallyspherical.
 8. A joint according to claim 5, wherein the inner face ofthe ball cage is internally spherical.